This work investigates the photolysis of 2,4-dinitrotoluene (2,4-DNT) in the presence of different dissolved species. Initial experiments revealed that the direct photolysis of 2,4-DNT in deionized water solutions under sunlight and artificial light followed a pseudo-first order kinetic. Humic acids (HA) appeared to act as sensitizers in the aqueous photolysis of 2,4-DNT and the calculated half life was found to be approximately 2 h, which is faster than the half life calculated in the case of deionized water (similar to 4 h). The presence of salt (NaCl) in the deionized water solutions was found to have a more pronounced sensitizing effect upon the photolysis of 2,4-DNT, yielding half lives of the order of I h. Investigations on seawater and groundwater spiked with 2,4-DNT, revealed that photolysis is enhanced in the order seawater > groundwater similar to deionized water. (c) 2007 Elsevier B.V. All rights reserved.